Perfluoroalkoxy copolymer coated glass and method of manufacturing same

ABSTRACT

An apparatus and method for coating glass, and specifically to perfluoroalkoxy copolymer coated glass and a method for manufacturing same. A glass substrate is placed on an electrically grounded support and cleaned with a solvent to remove impurities and prepare the surface of the substrate to be coated. The surface is coated with a primer and an electro-conductive enhancer is uniformly applied to the primer so that the surface of the glass substrate is wet, but not uneven. The perfluoroalkoxy copolymer is powder sprayed on the electro-conductive enhancer while the enhancer is still wet. The perfluoroalkoxy copolymer is secured to the glass substrate by evaporating the electro-conductive enhancer.

PRIORITY CLAIM

This application is a divisional of and claims the benefit of U.S.patent application Ser. No. 10/186,368, filed Jun. 27, 2002, the entirecontents are incorporated herein.

BACKGROUND OF THE INVENTION

The present invention relates in general to coated glass, andspecifically to perfluoroalkoxy copolymer coated glass and a method ofmanufacturing perfluoroalkoxy copolymer coated glass.

Coatings have been applied to glass to change one or morecharacteristics of the glass. One such coating is perfluoroalkoxycopolymer (“PFA”) which is one of the compounds sold by E.I. Du Pont deNemours and Company under the trademark Teflon®. PFA is most commonlyused as a non-stick coating on cookware such as pots and pans. PFA hasalso been used to coat glass such as automobile windshields and lightbulbs.

The structure of PFA makes it highly resistive to sticking or adheringto other substances. In particular, the structure of perfluoroalkoxycopolymer is a copolymer of tetrafluoroethylene (CF2=CF2) with aperfluoroalkoxy vinyl ether [F(CF2)m CF20CF−CF2]. The resultant polymercontains the carbon-fluorine backbone chain typical ofpolytetrafluoroethylene with perfluoroalkoxy side chains. The sidechains are connected to the carbon-fluorine backbone of the polymerthrough flexible oxygen linkages. The fluorine atoms in the chain resistalmost any other atom or molecule, even other fluorine atoms. As aresult, the fluorine atoms in PFA resist adhering to or even being nearother molecules. Thus, molecules at the surface of PFA repel the othermolecules and almost anything else that attempts to adhere or come closeto the PFA molecule. Additionally, the bond between the carbon andfluorine atoms is extremely strong. The bond is so stable that little toalmost nothing will react with it. Thus, PFA is a desirable coating tocoat glass products because it is a material, which minimally reactswith other compounds. PFA also includes very strong bonds between itsatoms which enables the coating to withstand extreme temperature andpressure conditions.

However, there are certain problems with known PFA coated glass. Oneknown problem is that although the PFA coats the glass, it does not forma strong bond with or strongly adhere to the glass because of its highlyresistive nature with respect to other molecules. Thus, when a glasssubstrate or glass product coated with PFA shatters or breaks, certainof the glass shards or pieces break away from the PFA coating. In somecoated glass products such as coated light bulbs, the PFA coating isapplied to the outside of the light bulb. When the light bulb coatedwith PFA breaks, the glass pieces remain inside the light bulb becausethe PFA layer creates a closed container such that the glass pieces arecontained inside the light bulb. However, other glass products such aslaboratory beakers are open glass containers. Therefore, the glassshards in these products can become loose and break away from thesurfaces of these products. The glass shards are unsafe and may causeinjury or severe injuries to users of these glass products.

Accordingly, there is a need for glass-coated materials and glassproducts that are coated with a material that has a very high bondstrength and which strongly adheres to glass. Additionally, there is aneed for a glass-coated materials and products that maintain thestructural integrity of the surfaces of the glass materials andproducts.

SUMMARY OF THE INVENTION

The present invention relates in general to coated glass, andspecifically to perfluoroalkoxy copolymer coated glass and a method ofmanufacturing perfluoroalkoxy copolymer coated glass.

One embodiment of the perfluoroalkoxy copolymer or PFA coated glass ofthe present invention includes a glass substrate, which may be anysuitable glass substrate, a layer of primer applied to the surface ofthe glass substrate being coated, an electro-conductive enhancer appliedto the primer and a layer of PFA applied to the electro-conductiveenhancer to form the coated glass substrate, wherein theelectro-conductive enhancer is evaporated to secure the PFA to thesurface of the glass substrate.

In one presently preferred embodiment of the method of the presentinvention, a glass substrate is positioned on an electrically conductivesupport. The surface of the glass substrate being coated is cleaned witha cleaner such as a solvent. In one embodiment, the solvent is methylethyl ketone (“MEK”). This solvent cleans and removes impurities whichmay be present on the surface of the glass substrate. In this step, thesolvent may be manually applied or mechanically applied to the glasssubstrate as desired by the manufacturer. Alternatively, the substratemay be pre-cleaned and the coating method may be performed in a suitable“clean room” where the cleaning step is not necessary.

In the next step, a layer of primer is applied to the surface of thesubstrate. The primer is applied as a mist or atomized spray so that acloudy or opaque appearance does not form on the surface of the glasssubstrate. After the primer is applied, the primer is cured using asuitable curing process. The curing process dries the primer andstrengthens the bonds between the primer and the surface of the glasssubstrate. In a presently preferred embodiment, the primer is cured at atemperature of approximately 500° F. (260° C.) for approximately fiveminutes. It should be appreciated that other suitable curing processesmay be employed in accordance with the present invention.

When the primer has been properly cured, an electro-conductive enhanceris applied on the primer on the surface of the glass substrate. In thepresently preferred embodiment, the enhancer is a highly polar solventwhich is electrically conductive. When the solvent is applied, the glasssubstrate becomes electrically grounded. By grounding the glasssubstrate, the solvent becomes charged and thereby attracts oppositelycharged particles. In one presently preferred embodiment, the solvent isa water soluble solvent such as N-methyl-2-pyrrolidone (NMP). In apresently preferred embodiment, the NMP layer is sprayed or applied tothe surface as a fog or mist so as to completely wet the surface of theglass substrate. However, the NMP layer is preferably applied so as toavoid forming a thick layer and avoid drippings which might detract fromthe bonding ability of the coatings.

While the solvent or NMP layer is still wet, a layer of PFA in powderform is sprayed over the wet NMP. The PFA particles have a charge whichis opposite to the charge of the NMP. Thus, the PFA particles areattracted to the NMP on the surface of the glass substrate. As a result,the PFA particles uniformly coat the surface of the NMP on the glasssubstrate. The PFA is applied to the NMP until the coatings on thesurface of the glass substrate achieve a desired thickness. In onepresently preferred embodiment, the desired thickness is approximately0.002 and 0.003 inches. Other suitable thickness ranges may be used asdesired by the manufacturer for other types of glass substrates or glassproducts.

Once the PFA layer is applied to the surface of the glass substrate, theNMP and PFA layers are heated, to evaporate the solvent or NMP from thesurface of the glass substrate and cure the PFA. In one embodiment, theNMP and PFA layers are heated to a temperature of approximately 800° F.(427° C.) for approximately twenty minutes. The heating processevaporates the NMP and cures the PFA layer which directly adheres to theprimer on the surface of the glass substrate. Because the PFA wasapplied to the wet solvent, the PFA is tightly packed and forms auniform coating on the surface of the glass substrate. As a result, thecoated glass substrate is clearer or more transparent and translucent.

It should be appreciated that the method of manufacturing or forming thePFA coated glass may be performed as described above by applying orspraying the coatings on to the surface of a glass substrate or glassproduct. Alternatively, the coatings may be applied using other suitablecoating methods. In one embodiment, the NMP layer is applied by dippingthe glass substrate in the NMP solvent. This coating process ensuresthat the surface of the glass substrate is completely coated with thesolvent.

It is therefore an advantage of the present to provide PFA coated glassand a method for manufacturing the PFA coated glass that maintains thestructural integrity of the glass.

Another advantage of the present invention is to provide a method formanufacturing coated glass which enables a perfluoroalkoxy copolymercoating to adhere to a glass substrate.

A further advantage of the present invention is to provide a method ofmanufacturing coated glass that forms a strong bond between aperfluoroalkoxy copolymer and a glass substrate.

Another advantage of the present invention is to provide a coated glasssubstrate and a method of manufacturing same that can be used on a widevariety of glass substrates and products.

Additional features and advantages of the present invention aredescribed in and will be apparent from, the following DetailedDescription of the Invention and the Figures.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A is an enlarged fragmentary side view of a coated glass substrateof one embodiment of the present invention.

FIG. 1B is an enlarged fragmentary cross-sectional view of the coatedglass substrate of FIG. 1A.

FIG. 2 is a flowchart illustrating one embodiment of the coating methodof the present invention.

FIG. 3A is an enlarged fragmentary side view of a coated glass substrateof one embodiment of the present invention illustrating the coated glasssubstrate before the solvent layer is evaporated.

FIG. 3B is an enlarged fragmentary cross-sectional view of the coatedglass substrate of FIG. 3A.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 1A, 1B, 2, 3A and 3B, one embodiment of thecoated glass product or substrate of the present invention isillustrated. The coated glass substrate or glass product 100 includes aglass substrate 102, a layer of primer 104 applied to at least oneportion, area or surface of the glass substrate and a layer of PFA 108applied to the primer layer on the surface of the glass substrate 102.This combination creates a very strong bond between the PFA and theprimer on the surface of the glass substrate and thereby enables the PFAlayer to adhere to and stretch with the glass substrate, whichsubstantially holds the glass substrate in tact. Additionally, thestrong bond formed between the PFA and the glass substrate enables thecoated glass substrate to withstand extreme conditions such as extremetemperatures and pressures. It should be appreciated that the glasssubstrate 102 may be any suitable type of glass substrate. Additionally,the glass substrate 102 may also be any suitable shape or configuration.

Referring now to FIGS. 2, 3A and 3B, in one presently preferredembodiment of the method of the present invention, the glass substrateis positioned on an electrically grounded support or holder as indicatedby block 200. In one embodiment, the grounded support is made of anelectrically conductive material such as metal and contacts and supportsthe glass substrate. In another embodiment, the grounded supportincludes a grounding plate or surface which supports and contacts asurface of the glass substrate. It should be appreciated that anysuitable grounding support may be used to support and ground the glasssubstrate.

Before any coatings are applied to the glass substrate, one or moresurfaces of the glass substrate 102 such as the outer surface of a glassbeaker, are cleaned using a suitable cleaner to remove all or asubstantial portion of the impurities from the surface of the glasssubstrate as indicated in block 201. In the presently preferredembodiment, the cleaner is a solvent such as methyl ethyl ketone(“MEK”). The cleaning of the surface of the glass substrate may beperformed manually or mechanically such as by a machine. It should beappreciated that other suitable cleaning methods and cleaners may beused to clean the surface of the glass substrate. It should also beappreciated that the surface of the glass substrate does not have to becleaned prior to applying the primer. For example, the glass substrateitself may be clean or substantially free of impurities prior toapplying the layers to the glass substrate. The layers are then appliedto the substrate in a clean room or a room virtually free fromimpurities. It should be appreciated that the glass substrate could alsobe manufactured in a clean room. It should further be appreciated thatthe glass substrate may be cleaned by a separate cleaning process or ina separate cleaning area prior to positioning the glass substrate on thegrounded support.

A layer of primer 104 is applied to the cleaned surface of the glasssubstrate as indicated by block 202. The primer may be any suitableprimer such as the 1200 clear primer manufactured by the Dow CorningCorporation. In a presently preferred embodiment, the primer is a clearprimer and is applied or sprayed onto the surface of the glass substrateas a mist or atomized spray. It should be appreciated that the primermay be applied using other suitable coating processes such as dippingthe substrate into a container of the primer. In this embodiment, thepurpose of applying the primer as a mist is to avoid or reduce thechances of the surface of becoming wet or saturated with the primer. Ifthe surface is wet or saturated with the primer, the appearance of thefinal coated glass substrate might appear cloudy or obscured due to thepooling of the primer on the surface of the glass substrate. Therefore,the pooling of the primer may also cause the surface to be uneven andinhibit light from passing through or cause refraction of the lightthrough the coated glass substrate. The obscure nature of the glasssubstrate may also inhibit a user from being able to see through thesubstrate. Therefore, a fine mist or atomized spray is preferablyapplied to the substrate in relatively small quantities over the surfaceof the substrate. The primer adheres to the surface of the glasssubstrate being coated and acts as a bonding agent for subsequentcoating layers. Once the primer is applied to the surface of the glasssubstrate, the primer is cured using a suitable curing process asindicated by block 204. In one embodiment, the primer is cured in anoven or other suitable heater. In another embodiment, the primer isair-dried to cure the primer. It should be appreciated that any suitablecuring process or method may be used to cure the primer in accordancewith the present invention. In the presently preferred embodiment, theprimer is cured by heating the primer with an oven or kiln to atemperature of approximately 500° F. (260° C.) for approximately fiveminutes.

After the primer has properly cured, an electro-conductive enhancer isapplied to the primer as indicated by block 206. In the presentlypreferred embodiment, the enhancer is a highly polarized solvent whichis electrically conductive. When the solvent is applied to the primerthe glass substrate becomes grounded. As a result, the solvent and theglass substrate develop a charge which attract materials or particleshaving an opposite charge. In one embodiment, the solvent is a watersoluble solvent. In another embodiment, the solvent isN-methyl-2-pyrrolidone (NMP), which is water soluble. In the presentlypreferred embodiment, the NMP solvent is applied as a fog spray onto theprimer layer 104 of the surface of the glass substrate 102. This processcontinues until the surface of the glass substrate is wet or completelycoated with the NMP.

While the layer of NMP is still wet, a layer of PFA is applied to thewet NMP layer. In the presently preferred embodiment, the PFA is appliedas particles which have an opposite charge from the NMP layer. Asdescribed above, the glass substrate is grounded, which promotes theflow of electric charge from the PFA layer to the solvent layer. Thevoltage differential causes the NMP layer to attract the oppositelycharged PFA particles to the NMP as indicated by block 208. This processcauses the PFA layer to uniformly coat the NMP layer without pooling orforming drips. Once the particles coat the solvent or NMP layer, theparticles act as an insulator against further particles accumulating onthe NMP layer. In a presently preferred embodiment, the PFA layer 108 ispowder sprayed and electrically attracted to the wet NMP layer until thethickness of the coatings on the glass substrate achieves a desiredthickness. Specifically, the desired thickness of the coatings isapproximately 0.002 to 0.003 inches. Once the PFA layer 108 is applied,the coated glass substrate includes three coating layers 104, 106 and108 as illustrated in FIGS. 3A and 3B. It should be appreciated that anysuitable thickness may be implemented with the present method based onthe desire of the manufacturer. Additionally, the PFA layer 108 mayinclude any suitable PFA coating such as 532-5010 or 5011 PFAmanufactured by E.I. Du Pont de Nemours and Company.

After the PFA layer 108 has been applied to the NMP layer 106 on thesurface of the glass substrate, the coated substrate is heated toevaporate the solvent layer and secure or adhere the PFA layer 108 tothe primer 104 on the surface of the glass substrate as indicated byblock 210. It should be appreciated that any suitable evaporation methodmay be employed to evaporate the solvent. It should also be noted thatthe solvent evaporates at a temperature of 400° F. (204° C.) and the PFAparticles or layer begins to melt and cure at 500° F. (260° C.). In apresently preferred embodiment, the layer is heated at a temperature ofapproximately 800° F. (427° C.) for approximately twenty minutes.Because the solvent evaporates at 400° F., the solvent evaporates firstas the coated substrate is heated. Once the solvent evaporates from thesurface of the coated glass substrate, the PFA remains and begins tomelt and cure on the surface of the glass substrate.

The PFA layer is tightly packed due to application of the PFA to the wetlayer of solvent. As a result, the PFA layer adheres directly to theprimer on the surface of the glass substrate when the solvent (NMP)evaporates from the surface of the glass substrate. This enables thefinal PFA coated glass substrate to have a much clearer appearance.Therefore, a user can see through the coated glass substrate and lightis able to pass through the coated glass substrate. These transparentand translucent characteristics of the coated glass substrate of thepresent invention enable the coated glass substrate and method of thepresent invention to be used for several commercial and industrialapplications such as light bulbs, home glassware, laboratory glassware,windows and windshields. Once the curing process is complete, the coatedglass substrate is transferred to another manufacturing area for furtherprocessing.

The method of the present invention creates very strong bonds betweenthe PFA and the primer on the surface of the glass substrate 102. As aresult, the PFA layer conforms to the glass and stretches to hold theglass surface together even when the glass shatters into several pieces.This prevents the glass from breaking up and falling away from the glasssurface. Therefore, the coated glass substrates and products producedaccording to the present invention are very durable and resistantbreaking apart, which makes the coated glass substrate of the presentinvention suitable for several different applications. For example, thePFA coated glass substrate may be used for laboratory glassware such asa test tube or beaker. The strength of the bonds created between the PFAlayer 108 and the surface of the glass substrate 102 enables the glasssurface of the laboratory glassware to substantially maintain itsstructural integrity upon shattering or breaking. This is very importantfor safety purposes because injuries or potentially serious injuries canbe minimized or prevented. Also, the strength of the PFA bonds enablesthe coated glass to withstand high pressure and temperature cleaningsystems found in laboratories and hospitals.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

1. A coated glass substrate comprising: a glass substrate; a layer ofprimer secured to said substrate; and a layer of perfluoroalkoxycopolymer secured to the primer, said layer of perfluoroalkoxy copolymerapplied to the primer using a layer of electro-conductive enhancer andsecured to the primer by evaporating the layer of electro-conductiveenhancer.
 2. The coated glass substrate of claim 1, wherein the primerlayer includes a clear primer.
 3. The coated glass substrate of claim 1,wherein the primer layer is substantially transparent.
 4. The coatedglass substrate of claim 1, wherein the primer layer is substantiallytranslucent.
 5. The coated glass substrate of claim 1, wherein the layerof electro-conductive enhancer includes a solvent.
 6. The coated glasssubstrate of claim 1, wherein the layer of electro-conductive enhancerincludes a water-soluble solvent.
 7. The coated glass substrate of claim6, wherein the water soluble solvent is N-methyl-2 pyrrolidone.
 8. Thecoated glass substrate of claim 1, wherein the perfluoroalkoxy copolymeris powdered perfluoroalkoxy copolymer.
 9. The coated glass substrate ofclaim 1, wherein a thickness of the layers on the glass substrate isincluded in a predetermined range of thicknesses.
 10. The coated glasssubstrate of claim 9, wherein the range of thicknesses is approximately0.002 to 0.003 inches.
 11. The coated glass substrate of claim 1,wherein the glass substrate is selected from the group consisting of: alight bulb, a beaker, a test tube, a home glassware, a laboratoryglassware, a window and a windshield.
 12. A coated glass substratecomprising: a glass substrate; a layer of primer secured to saidsubstrate; and a layer of a fluorocopolymer secured to the primer, saidlayer of fluorocopolymer applied to the primer using a layer ofelectro-conductive enhancer and secured to the primer by evaporating thelayer of electro-conductive enhancer.
 13. The coated glass substrate ofclaim 12, wherein the primer layer includes a clear primer.
 14. Thecoated glass substrate of claim 12, wherein the primer layer issubstantially transparent.
 15. The coated glass substrate of claim 12,wherein the primer layer is substantially translucent.
 16. The coatedglass substrate of claim 12, wherein a thickness of the layers on theglass substrate is included in a predetermined range of thicknesses. 17.The coated glass substrate of claim 16, wherein the range of thicknessesis approximately 0.002 to 0.003 inches.
 18. The coated glass substrateof claim 12, wherein the glass substrate is selected from the groupconsisting of: a light bulb, a beaker, a test tube, a home glassware, alaboratory glassware, a window and a windshield.